JP2003329314A - Air conditioner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an air conditioner wherein both durability and refrigerating capacity are improved. <P>SOLUTION: This air conditioner 1 is provided with: a compressor 2 for compressing a refrigerant; a radiator 3 for cooling the refrigerant compressed by the compressor 2; a decompressor 4 for decompressing the refrigerant cooled by the radiator 3; and an evaporator 5 for evaporating the refrigerant decompressed by the decompressor 4, and composes a refrigerating cycle by using carbon dioxide as the refrigerant. The air conditioner is characterized by having a supply passage 8 for supplying the refrigerant cooled by the radiator 3 into a compression process of the compressor 2. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air conditioner using carbon dioxide as a refrigerant instead of a CFC refrigerant.

[0002]

2. Description of the Related Art In recent years, there has been an increasing interest in preserving the global environment, but R used as a refrigerant for air conditioners
CFC refrigerants such as 134a are feared to promote global warming. For this reason, studies have been conducted on an air conditioner using a substance that originally exists in nature, that is, a so-called natural refrigerant, as a substance that replaces such a CFC refrigerant.

As a candidate for such a CFC substitute, carbon dioxide (hereinafter referred to as CO ₂ ) is drawing attention. CO ₂
Is highly valued not only for its far smaller impact on global warming than CFCs, but also for its nonflammability and basically harm to the human body.

From such a background, a vapor compression refrigeration cycle using CO ₂ (hereinafter referred to as a CO ₂ refrigeration cycle) has been proposed. The operation of this CO ₂ refrigeration cycle is the same as that of the conventional vapor compression refrigeration cycle using Freon. That is, as shown in CO ₂ Mollier diagram of FIG. 3, compressed by the compressor of CO ₂ cold low pressure (gas phase) (A-B), the gas phase of high temperature and high pressure. Next, high-temperature and high-pressure CO ₂ (gas phase state) is cooled by a radiator (BC), and decompressed by a decompressor (C-
D), low temperature and low pressure gas-liquid two-phase state. Next, low-temperature low-pressure CO ₂ (gas-liquid two-layer state) is evaporated by an evaporator (D-
A), the evaporation latent heat generated at that time is taken from the external fluid such as air to cool the external fluid.

It should be noted that CO ₂ undergoes a phase change to a gas-liquid two-layer state when the pressure falls below the saturated vapor pressure (the pressure at the intersection of the line segment CD and the saturated liquid line SL). The state in which the pressure exceeds the saturated vapor pressure at the critical temperature is called the supercritical state, and when the state slowly changes from the state C to the state D, CO ₂ changes from the supercritical state to the liquid state and then vaporizes. The liquid changes to a two-layer state. By the way, the supercritical state means a state in which CO ₂ molecules move like a gas phase state while the density is almost equal to the liquid density.

However, the critical temperature of CO ₂ is about 31 ° C., which is the critical temperature of conventional CFCs (for example, R134a has a critical temperature of 101 ° C.).
Since ° C.) lower than, CO ₂ at the radiator side in summer or the like
The temperature becomes higher than the critical temperature of CO ₂ . That is, CO ₂ does not condense even on the radiator outlet side (the line segment BC does not intersect with the saturated liquid ship SL). The state on the radiator outlet side (point C) is determined by the discharge pressure of the compressor and the CO ₂ temperature on the radiator outlet side. The CO ₂ temperature on the radiator outlet side is the heat radiation capacity of the radiator. And the outside temperature. Since the outside air temperature cannot be controlled, the CO ₂ temperature at the radiator outlet side cannot be substantially controlled.

Therefore, the state on the radiator outlet side (point C) can be controlled by controlling the discharge pressure of the compressor (radiator outlet side pressure). That is, when the outside air temperature (heat load) is high in summer, etc., E-F-G-H- in FIG.
As indicated by E, the radiator outlet side pressure needs to be increased.

In this way, in order to adjust the radiator outlet side pressure (hereinafter referred to as the high pressure side pressure), the refrigerant filling amount of the high pressure side in the CO ₂ refrigeration cycle is adjusted to adjust the high pressure side pressure. Has been proposed (see, for example, Japanese Patent Publication No. 7-18602). In this CO ₂ refrigeration cycle, a compressor that compresses a refrigerant, a radiator that cools the refrigerant compressed by the compressor, a throttle valve that depressurizes the refrigerant cooled by the radiator, and a refrigerant that depressurizes by the throttle valve evaporates An evaporator that vaporizes and a receiver that separates the vaporized refrigerant and the liquid refrigerant are provided, and a countercurrent type that heat-exchanges between the refrigerant cooled by the radiator and the vaporized refrigerant that is gas-liquid separated by the receiver. A heat exchanger and a liquid phase line for guiding the liquid refrigerant from the receiver to the front or the rear of the countercurrent heat exchanger are provided.

According to the above construction, the refrigerant is compressed by the compressor, the compressed refrigerant is cooled by the radiator, and the countercurrent heat exchanger exchanges heat with the vaporized refrigerant separated by the receiver described later. And further cool. Since the refrigerant cooled by the radiator is further cooled, the enthalpy change amount during the evaporation process becomes large. The cooled high-pressure refrigerant is decompressed by a throttle valve to become a low-temperature low-pressure gas-liquid two-phase refrigerant, which is heat-exchanged with an external fluid by an evaporator and evaporated and vaporized. The refrigerant vaporized in the evaporator is separated into gas and liquid by the receiver, and the vaporized refrigerant separated by the receiver is further cooled by the radiator cooled by the radiator in the countercurrent heat exchanger, and again by the compressor. Compressed. Further, the liquid phase line functions to return the lubricating oil accumulated in the receiver into the circuit.

Aside from this, there has been proposed a technique for suppressing the high pressure side pressure without impairing the refrigerating capacity (see, for example, Japanese Patent Laid-Open No. 10-288411). This CO ₂
The refrigeration cycle includes a compressor that compresses the refrigerant, a radiator that cools the compressed refrigerant, a second decompression device that decompresses the cooled refrigerant, and an evaporator that evaporates and vaporizes the refrigerant decompressed by the second decompression device. A first pressure reducing device that includes an accumulator that separates the refrigerant vaporized by the evaporator from the liquid refrigerant, branches a part of the refrigerant cooled by the radiator, and depressurizes the branched refrigerant; and a first pressure reducing device. A cooler that exchanges heat between the refrigerant that has been depressurized in step 1 and the refrigerant that has been cooled in the radiator, and a return flow path that returns the refrigerant that has exchanged heat in the radiator and that has been depressurized by the first depressurizer to the middle of the compression process of the compressor And are provided.

According to the above construction, the refrigerant is compressed by the compressor, the compressed refrigerant is cooled by the radiator, and
It is further cooled by exchanging heat with the refrigerant decompressed by the first decompression device described later. Since the refrigerant cooled by the radiator is further cooled, the enthalpy change amount during the evaporation process becomes large. The cooled high-pressure refrigerant is decompressed by the second decompression device to be a low-temperature low-pressure gas-liquid two-phase refrigerant, which is heat-exchanged with the external fluid by the evaporator and evaporated and vaporized. The refrigerant vaporized by the evaporator is separated into gas and liquid by the accumulator, and the vaporized refrigerant separated by the accumulator is compressed again by the compressor.

Further, a part of the refrigerant cooled by the radiator is branched and decompressed by the first decompressor into a low-temperature low-pressure gas-liquid two-phase refrigerant, and the refrigerant cooled by the radiator is further cooled by the cooler. To do. After that, the refrigerant that has exchanged heat and vaporized is returned to the middle of the compression process of the compressor through the return flow path. Part of the heat generated in the refrigerant compression step is taken by the supplied refrigerant, and the temperature of the finally discharged refrigerant is reduced by the taken heat.

[0013]

By the way, Japanese Patent Publication No. 7-
In the example of 18602 public information, in the countercurrent heat exchanger,
Since heat is exchanged between the refrigerant cooled by the radiator and the vaporized refrigerant separated by the receiver, the temperature of the vaporized refrigerant becomes high. When the refrigerant having a high temperature is compressed by the compressor, the temperature of the discharged refrigerant also becomes high, so that the operating temperature of the compressor becomes high and the durability of the compressor may be deteriorated. Further, in the example of Japanese Patent Laid-Open No. 10-288411, since the refrigerant to be returned to the compression step of the compressor is a vaporized refrigerant having a low density, as a method of increasing the refrigerating capacity, the refrigerant filling amount on the high pressure side is increased to increase the refrigeration capacity. There was a problem that it was disadvantageous to increase the pressure.

The present invention has been made in consideration of such circumstances, and an object thereof is to provide an air conditioner which can improve both durability and refrigerating capacity.

[0015]

In order to solve the above problems, the air conditioner of the present invention employs the following means.
The invention according to claim 1 includes a compressor for compressing a refrigerant, a radiator for cooling the refrigerant compressed by the compressor, a decompressor for decompressing the refrigerant cooled in the radiator, and the decompressor. An air conditioner comprising a vaporizer for evaporating a decompressed refrigerant, wherein carbon dioxide is used as a refrigerant to constitute a refrigeration cycle, and the refrigerant cooled in the radiator is supplied to a compression step of the compressor. It is characterized by having a supply path for

According to the air conditioner of the present invention,
By supplying the refrigerant cooled in the radiator to the compression step of the compressor, part of the heat generated in the refrigerant compression step is taken away by the supplied refrigerant, and the temperature of the refrigerant finally discharged. Is lower by the amount of heat taken away, and the operating temperature of the compressor is lower. Further, since the refrigerant supplied to the compression step is in a supercritical state, its density is high and CO ₂
Since the effect of increasing the refrigerant filling amount on the high pressure side of the refrigeration cycle to increase the pressure on the high pressure side, that is, the effect of increasing the enthalpy change amount in the evaporation process is large, the refrigerant has a large ability to remove heat from the external fluid and a large refrigerating capacity. Become.

According to a second aspect of the present invention, in the air conditioner according to the first aspect, there is provided a heat exchanger for exchanging heat between the refrigerant cooled by the radiator and the refrigerant vaporized by the evaporator. An air conditioner characterized by comprising.

According to the air conditioner of the present invention,
As for the refrigerant cooled by the radiator and the refrigerant vaporized by the evaporator, the refrigerant cooled by the radiator has a higher temperature than the refrigerant vaporized by the evaporator. Since the refrigerant cooled by the vessel is further cooled and the amount of change in enthalpy in the evaporation process is further increased, the refrigerant's ability to remove heat from the external fluid and its refrigerating ability are increased.

According to a third aspect of the present invention, in the air conditioner according to the first or second aspect, the air conditioner is characterized by interposing a flow rate adjusting unit for adjusting the flow rate of the refrigerant flowing through the supply passage. .

According to the air conditioner of the present invention,
Since the flow rate of the refrigerant supplied to the compression process of the compressor is arbitrarily adjusted by the function of the flow rate controller, the temperature of the refrigerant discharged from the compressor is also arbitrarily determined. In addition, the refrigerant charge on the high pressure side of the CO ₂ refrigeration cycle can be adjusted as desired.
The pressure on the high pressure side can also be adjusted arbitrarily. Finally, the amount of change in enthalpy during the evaporation process can be adjusted arbitrarily.

According to a fourth aspect of the present invention, in the air conditioner according to the third aspect, a temperature sensor for detecting the temperature of the refrigerant discharged from the compressor is provided, and the supply based on the output of the temperature sensor. An air conditioner characterized by controlling the flow rate of a refrigerant flowing in a passage.

According to the air conditioner of the present invention,
Based on the output of the temperature sensor that detects the temperature of the refrigerant discharged from the compressor, the temperature of the refrigerant discharged from the compressor is controlled by controlling the flow rate of the refrigerant that flows through the supply path and is supplied to the compression process. However, the temperature is automatically adjusted below a certain temperature.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a first configuration of an air conditioner that constitutes a refrigeration cycle using CO ₂ as a refrigerant instead of CFC. 1, an air conditioner 1 includes a compressor 2 that compresses a refrigerant, a radiator 3 that cools the compressed refrigerant, a decompressor 4 that decompresses the refrigerant cooled by the radiator 3, and an evaporator that decompresses the decompressed refrigerant. Evaporator 5 that evaporates, accumulator 6 that separates the refrigerant and liquid refrigerant that are vaporized in evaporator 5, and the countercurrent heat exchange that exchanges heat between the refrigerant cooled by radiator 3 and the vaporized refrigerant separated by accumulator 6. And a container 7.

The air conditioner is provided with a supply passage 8 extending from between the radiator 3 and the countercurrent heat exchanger 7 to the compression process of the compressor 2. A solenoid valve (flow rate adjusting unit) 9 and a fixed throttle (flow rate adjusting unit) 10 for adjusting the flow rate of the refrigerant are provided in the supply passage 8, and a temperature for measuring the discharge temperature of the refrigerant is provided on the discharge side of the compressor 2. A sensor 11 is provided. Temperature sensor 1
The output of 1 controls the opening / closing of the solenoid valve 9.

In the air conditioner 1 having the above structure, as shown in FIG. 1, the refrigerant is compressed by the compressor 2, the compressed refrigerant is cooled in the radiator 3, and the cooled refrigerant is countercurrent. In the mold heat exchanger 7, heat is exchanged with the vaporized refrigerant that has been gas-liquid separated by the accumulator 6 described later, and is further cooled. Since the coolant cooled by the radiator 3 is further cooled, the enthalpy change amount in the evaporation process becomes large. The cooled high-pressure refrigerant is decompressed by the decompressor 4 to be a low-temperature low-pressure gas-liquid two-phase refrigerant, which is evaporated and vaporized by exchanging heat with the external fluid in the evaporator 5. The refrigerant vaporized in the evaporator 5 is separated into gas and liquid by the accumulator 6, and the vaporized refrigerant separated by the accumulator 6 is further cooled by the countercurrent heat exchanger 7 in the radiator 3. Then, it is compressed again by the compressor 2.

Further, a part of the refrigerant cooled by the radiator 3 is branched, and the branched refrigerant remains in the supercritical state and the supply path 8
And is returned to the middle of the compression process of the compressor 2. Part of the heat generated in the refrigerant compression step is taken by the supplied refrigerant, and the temperature of the finally discharged refrigerant is reduced by the taken heat.

The temperature of the refrigerant discharged from the compressor 2 is detected by the temperature sensor 11, the opening / closing of the solenoid valve 9 is controlled based on the output of the temperature sensor 11, and the opening / closing of the solenoid valve 9 and the fixed throttle 10 are used for compression. By controlling the flow rate of the refrigerant supplied to the process, the temperature of the refrigerant discharged from the compressor 2 becomes
Automatically kept constant.

According to the above configuration, since the refrigerant cooled in the radiator 3 is supplied to the compression process of the compressor 2, part of the heat generated in the refrigerant compression process is taken by the supplied refrigerant. Then, the temperature of the finally discharged refrigerant becomes lower by the amount of heat taken away. Therefore, the operating temperature of the compressor 2 is lowered, and the durability of the compressor 2 can be improved.

At the same time, since the refrigerant supplied to the compression step is in a supercritical state, its density is high, and the refrigerant filling amount on the high pressure side of the CO ₂ refrigeration cycle is increased to increase the pressure on the high pressure side. The effect of increasing the amount of change in enthalpy during the evaporation process is great, and the refrigerating capacity can be improved.

Further, the flow rate of the refrigerant supplied to the compression process is controlled by the opening / closing of the solenoid valve 9 and the fixed throttle 10 based on the output of the temperature sensor for detecting the temperature of the refrigerant discharged from the compressor 2. Then, since the temperature of the refrigerant discharged from the compressor 2 is automatically adjusted to a certain temperature or less, the operating temperature of the compressor 2 is also automatically adjusted to a certain temperature or less, and the failure of the compressor 2 is caused. That is, it is possible to improve durability.

In FIG. 2, CO ₂ as an alternative to CFCs
The 2nd structure of the air conditioning apparatus which comprises a refrigerating cycle by using as a refrigerant is shown. In FIG. 2, the basic configuration of the air conditioner 20 is the same as that shown in FIG. 1, and the same components are assigned the same reference numerals and explanations thereof are omitted. In FIG. 2, a supply passage 8 has a variable throttle 2 for adjusting the flow rate of the refrigerant.
1 is installed.

In the air conditioner 20 having the above structure, as shown in FIG. 2, the refrigerant is compressed by the compressor 2, the compressed refrigerant is cooled in the radiator 3, and the cooled refrigerant is countercurrent. In the mold heat exchanger 7, heat is exchanged with the vaporized refrigerant that has been gas-liquid separated by the accumulator 6 described later, and is further cooled. Since the coolant cooled by the radiator 3 is further cooled, the enthalpy change amount in the evaporation process becomes large. The cooled high-pressure refrigerant is decompressed by the decompressor 4,
The low-temperature low-pressure refrigerant in a gas-liquid two-phase state is heat-exchanged with an external fluid in the evaporator 5 to be evaporated and vaporized. The refrigerant vaporized in the evaporator 5 is separated into gas and liquid by the accumulator 6,
The vaporized refrigerant separated into gas and liquid by the accumulator 6 further cools the refrigerant cooled by the radiator 3 in the countercurrent heat exchanger 7, and is compressed again by the compressor 2.

Further, a part of the refrigerant cooled by the radiator 3 is branched, and the branched refrigerant remains in the supercritical state and the supply path 8
And is returned to the middle of the compression process of the compressor 2. Part of the heat generated in the refrigerant compression step is taken by the supplied refrigerant, and the temperature of the finally discharged refrigerant is reduced by the taken heat.

The temperature of the refrigerant discharged from the compressor 2 is detected by the temperature sensor 11, the opening of the variable throttle 21 is controlled based on the output of the temperature sensor 11, and the opening of the variable throttle 21 causes the compression process. By controlling the flow rate of the supplied refrigerant more finely, the temperature of the refrigerant discharged from the compressor 2 tends to be automatically kept constant.

According to the above construction, since the refrigerant cooled in the radiator 3 is supplied to the compression step of the compressor 2, part of the heat generated in the refrigerant compression step is taken by the supplied refrigerant. Then, the temperature of the finally discharged refrigerant becomes lower by the amount of heat taken away. Therefore, the operating temperature of the compressor 2 is lowered, and the durability of the compressor 2 can be improved.

At the same time, since the refrigerant supplied to the compression step is in a supercritical state, its density is high, and the refrigerant filling amount on the high pressure side of the CO ₂ refrigeration cycle is increased to increase the pressure on the high pressure side. The effect of increasing the amount of change in enthalpy during the evaporation process is great, and the refrigerating capacity can be improved.

Further, based on the output of the temperature sensor for detecting the temperature of the refrigerant discharged from the compressor 2, the variable throttle 21
The temperature of the refrigerant discharged from the compressor 2 is automatically adjusted to a certain temperature or less by controlling the flow rate of the refrigerant supplied to the compression process more finely according to the opening degree of the operation of the compressor 2. The temperature is also automatically adjusted to be equal to or lower than a certain temperature, so that failure of the compressor 2 can be prevented, that is, durability can be further improved.

In the above-described embodiment, the route of the supply path 8 has been described as being adapted to the solid line in FIGS. 1 and 2, but the route of the supply path 8 is indicated by the solid line in FIGS. The same effect can be obtained even if the route of the supply path 8 is not limited to the one shown in FIG. 1 and FIG.

Further, in the above-described embodiment, the temperature sensor has been described as being applied to the compressor discharge part, but the temperature sensor is not limited to that provided in the compressor discharge part. Instead, the temperature sensor may be provided at any point between the compressor discharge portion and the pressure reducer inlet.

[0040]

As described above, according to the first aspect of the present invention, by supplying the refrigerant cooled in the radiator to the compression step of the compressor, the heat generated in the refrigerant compression step is reduced. The part is taken by the supplied refrigerant, and the temperature of the finally discharged refrigerant becomes lower by the amount of the taken heat. Therefore, the operating temperature of the compressor is lowered, the durability of the compressor is improved, and at the same time, the refrigerant supplied to the compression step is in a supercritical state, so that its density is high and the high pressure side of the CO ₂ refrigeration cycle is high. The effect of increasing the refrigerant charge amount to increase the pressure on the high pressure side, that is, the effect of increasing the enthalpy change amount in the evaporation process is large. Therefore, there is an effect that the ability of the refrigerant to remove heat from the external fluid and the refrigerating ability are improved.

According to the second aspect of the present invention, of the refrigerant cooled by the radiator and the refrigerant vaporized by the evaporator, the refrigerant cooled by the radiator has a higher temperature than the refrigerant vaporized by the evaporator. Therefore, due to the heat exchange in the heat exchanger, the refrigerant cooled by the radiator is further cooled, the enthalpy change amount in the evaporation process is further increased, and the refrigerating capacity is further improved.

According to the third aspect of the invention, since the flow rate of the refrigerant supplied to the compression step of the compressor is arbitrarily adjusted by the function of the flow rate adjusting section, the temperature of the refrigerant discharged from the compressor is also arbitrary. Stipulated in. Therefore, the operating temperature of the compressor is also arbitrarily set, failure of the compressor can be prevented, and durability can be improved. At the same time, the amount of refrigerant charged on the high-pressure side of the CO ₂ refrigeration cycle, and by extension, the high-pressure side, can be reduced. Since the pressure can be adjusted arbitrarily and the amount of change in enthalpy in the evaporation process can be adjusted arbitrarily, the refrigerating capacity can be arbitrarily increased.

According to the fourth aspect of the invention, the compressor is controlled by controlling the flow rate of the refrigerant supplied to the compression process based on the output of the temperature sensor that detects the temperature of the refrigerant discharged from the compressor. Since the temperature of the refrigerant discharged from is automatically adjusted to a certain temperature or less, the operating temperature of the compressor is also automatically adjusted to a certain temperature or less, preventing failure of the compressor and durability. There is an effect of improving.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of an air conditioner according to the present invention.

FIG. 2 is a schematic configuration diagram showing another embodiment of the air conditioner according to the present invention.

FIG. 3 is a Mollier diagram of a refrigeration cycle realized by a conventional air conditioner that uses carbon dioxide as a refrigerant.

[Explanation of symbols]

1,20 Air conditioner 2 compressor 3 radiator 4 pressure reducer 5 evaporator 7 Countercurrent heat exchanger (heat exchanger) 8 supply routes 9 Solenoid valve (flow rate control unit) 10 Fixed throttle (flow rate control unit) 11 Temperature sensor 21 Variable throttle (flow rate controller)

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Takayuki Hagita             1 Takamichi, Iwatsuka-cho, Nakamura-ku, Nagoya-shi, Aichi               Mitsubishi Heavy Industries Nagoya Research Center

Claims (4)

[Claims] 1. A compressor for compressing a refrigerant, a radiator for cooling the refrigerant compressed by the compressor, a decompressor for decompressing the refrigerant cooled in the radiator, and a decompressor for decompressing the refrigerant. An air conditioner that comprises an evaporator that evaporates a refrigerant and that constitutes a refrigeration cycle using carbon dioxide as a refrigerant, and is a supply path that supplies the refrigerant cooled in the radiator to a compression step of the compressor. An air conditioner characterized by having. 2. The air conditioner according to claim 1, further comprising a heat exchanger that exchanges heat between the refrigerant cooled by the radiator and the refrigerant vaporized by the evaporator. Air conditioner. 3. The air conditioner according to claim 1, further comprising a flow rate adjusting unit for adjusting a flow rate of the refrigerant flowing in the supply passage. 4. The air conditioner according to claim 3, further comprising a temperature sensor that detects the temperature of the refrigerant discharged from the compressor, and based on the output of the temperature sensor, the amount of the refrigerant flowing in the supply passage. An air conditioner characterized by controlling the flow rate.